Gas burner with modulated flame orifice



Oct. 23, 1951 Filed April 7, 1947 GAS BURNER WITH MODULATED FLAMEORIFICE 2 SHEETSSHEET l 46 54 25 45 17 54 11 19 "n n l -u INVENTOR. H61944/4 F .fi'wzmsav BY AM new A Pvnvon Patented Oct. 23, 1951 GAS BURNERWITH MQDULATED FLAME ORIFICE Paul F. Swenson, Cleveland Heights, andMilton F. Pravda, Redford, Ohio, assignors to The Cleveland ResearchCorporation, Cleveland,

Application April 7 1947, Serial No."739,738

'7 Claims. 1

This invention relates to gas "burners and more specifically to gasburners of the so called "modulating type in which the gas discharge isincreased and decreased'gradually in response to the heat requirementsof a room or space being heated, as distinguished from a burner of theon and off type in which the gas discharge is intermittently turned onand off in response to the heat requirements.

Attempts have been made heretofore to provide amodulating gas burnerbut, so far as these applicants are aware, none of the attempts haveproven practical or satisfactory. One disadvantage in the modulatingburner heretofore provided has been that when the burner had numerousdischarge openings for the gas and air mixture and the gas supply to theburner was throttled down to a condition corresponding with a low heatrequirement, the flame could not be sustained at all of the dischargeopenings. resulted in the issuance of unburned gas'from certain of theopenings and the unburned gas passing up the flue was not onlyuneconomical u cr at d a d n er u cond t on Mo eover, the burn n of t mx u r o ly a po t on of the burner openings also created a condition inwhich a complete extinguishment of the flame could easily be produced bythe occurrence of a down-draft.

To eliminate the undesirable condition just described attempts have beenmade to construct a modulating gas burner with fewer burner openings andto make the burner openings of larger size. Another disadvantage wasthen encountered in that when the gas discharge in the burner wasthrottled down to a condition-corresponding with a low heat requirement,hackfires in the burner were a frequent occurrence. The backfires causedthe gas to burn at the dis charge orifice instead of at the burneropenings and this also created an unsatisfactory and hazardouscondition.

The present invention provides an improved modulating gas burner of asimple andinexpensive construction capable of functioning :in a safe andeconomical manner and in which the above and other disadvantagesareovercome.

Another object of this invention is to provide a modulating gas burnerin which the gas stream and the gas and air mixture stream are variedsimultaneously .so that an efiicient and depend:- able "functioning willbe obtained throughout substantially the entire range of burneroperation.

A further object of the inventionis to. provide a modulating gas burnerin which the :size .of the 2 as delivery orifice and the size of the gasand air mixture discharge opening are varied simultaneously by graduallyincreasing or decreasing the same. V

Still another object is to provide a gas burner of the charactermentioned, in which the gas delivery orifice, the gas and air mixturedischarge opening and the combustion air passage are variedsimultaneously bygradually increasing or decreasing the same.

Yet another object is to provide a gas burner of this character, inwhich gas pressure responsive means is employed for varying the gasstream, the mixture stream and the supply of combustion air.

A further object is to provide a gas burner of this character, in whichtemperature responsive means is employed for controlling the variationbeing produced in the gas stream, the mixture stream and the combustionair stream, by the gas pressure responsive means.

As "another of itsob'jects this invention provides an improved gasburner of the character mentioned, in which'the volume of the gas streamand the volume of the gas and air mixture stream can be simultaneouslyvaried gradually and throughout substantially the entire range of burneroperation in response to heat requirements but in which a desireddischarge velocity is maintained for these streams such that a safeandefiicient functioning of the burner will be obtained at all times.

The invention can be further briefly summarized asconsisting in certainnovel combinations and arrangements of parts, hereinafter describedandparticularly set out in the appended claims.

In-the accompanying sheets of drawings,

Fig. l is an elevational View, mainly in vertical section, showing amodulating gas burner embodying the present invention, the view alsoincluding control devices associated with the :burner and :which arelikewise shown in sections :Eig. 2.is. a partial vertical sectional.view taken through the upper portion of the pilot burner and showingthis portion on .a larger scale.

Fig. .3 is .a partial vertical sectional view-taken through the lowerportionof the pilot burner and showing this portion on a larger scale,and

jfilighe is an elevational View, mainly in vertical section, showinganother modulatin as burner embodying the present invention.

.-.As one practical embodiment of the invention Fig. 1 shows amodulating gas burner III which comprises, general, a hollow casing Hand a pair.ofxgcoaxialouternnd inner burner tubes 12 3 and I3. In thisinstance the burner I is shown in an upright position in which thecasing N forms the base of the unit and the burner tubes I2 and I3extend substantially vertically above the casing. It will be understoodof course that a modulating gas burner embodying the samecharacteristics and features as the burner II] can be designed foroperation in a horizontal position or in any other desired position orlocation.

The burner I0 is also shown in this instance as being installed in adomestic furnace or the like F which is here represented by the sidewall portion I4 and the refractory slab l5. It should be understood,however, that the burner I0 is applicable to all kinds of heatingservice and can be used for any desired purpose.

The outer burner tube I2 is supported by the casing I and has itsoutwardly flared lower end |2a connected therewith as by means of thescrews I6. The lower end of this outer burner tube is spaced from thecasing so as to provide therebetween an annular air inlet opening I1.The burner tube can be maintained in this relation to the casing II bysuitable spacers I8 through which the screws I6 extend. The upper end ofthe burner tube I2 extends into an opening |a of the refractory slab I5and carries a deflector plate I9. The deflector plate extendstransversely of th open upper end of the burner tube I2 and is mountedthereon as by a plurality of circumferentially spaced axial arms 2|. Asecond refractory slab 22 is supported by the deflector plate I9 andheld thereby in spaced relation above the refractory slab I5, The slab22 has a central opening 22a therein and can be maintained in positionon the deflector plate I9 by means of a stem I9a. provided on the latterand which engages in this central opening.

The casing II has a gas supply connection 24 connected therewith in theform of a pipe which extends to a suitable source of gas under pressure.The casing also has a gas delivery nozzle 25 mounted on the upper sidethereof and located substantially on the common axis of the burner tubesI2 and I3. The nozzle 25 is supplied with gas from the connection 24through the casing I I, as will be explained in detail hereinafter, andhas an outwardly converging orifice or passage 26 for discharging astream of gas axially of the burner tubes.

The inner burner tube I3, which is at times referred to as a mixingtube, extends longitudinally in the outer burner tube I2 and is spacedtherefrom so as to provide therebetween an annular passage 21 forsecondary combustion air. The tube I3 has approximately the shape of aVenturi tube and is disposed with its outwardly flared lower end 3alocated immediately above the nozzle 25 so that the discharge of avelocity stream of gas from the nozzle will induce a flow of primarycombustion air into such lower end for mixing with the gas. The upperend of the tube I3 has an outwardly flared portion |3b which is disposedin adjacently spaced relation to the deflector plate |9 so as to providetherebetween an annular space or discharge opening 29 for the gas andair mixture and from which the gas and air mixture issues as a velocitystream and burns as a sustained flame. The flame produced by thisvelocity mixture stream travels away from the discharge opening 29 inlaterally spreading relation adjacent the underside of the refractoryslab 22.

The volum of the gas stream being delivered by the nozzle 25 is variedin accordance with the heat requirements of the room or space beingheated by the burner I0. This variation of the gas stream isaccomplished by gradually varying the effective size of the orificeopening 26 by means of a movable valve element 3| which cooperates withthe nozzle 25 in forming a metering valve for the gas. The valve element3| is preferably in the form of the needle valve element here shown andwhich has an outwardly converging portion 3|a which is movable in andcooperates with the tapered nozzle 25 for varying the effective size, ofthe orifice opening 26.

The volume of the gas and air mixture stream is varied simultaneouslywith, and in corresponding relation to, the variation in the volume ofthe gas stream being delivered from the nozzle 25. For this purpose themixing tube I3 is movable axially of the burner unit so as to vary thespacing of its flared upper end I3b' relative to the deflector plate I9.The mixing tube I3 is adapted to be shifted by the movement which isimparted to the valve element 3| for varying the gas stream and, to thisend, the valve element has an upwardly extending stem extension 311) onwhich the mixing tube I3 is mounted as by means of the spider 32.

With the construction and arrangement just described it will be seenthat when the valve element 3| is moved upwardly, that is, in adirection outwardly of the nozzle 25 to decrease the volume of thestream of gas being delivered from the nozzle, the mixing tube I3 willalso be moved upwardly causing its flared end |3b to approach thedeflector plate I9 and thereby decrease the size of the gas and airmixture discharge opening 29. Conversely, when the valve element 3| ismoved in the opposite direction, that is, inwardly of the nozzle 25 toincrease the size of the orifice opening 23 and the volume of the gasstream being discharged therefrom, the flared upper end |3 b of themixing tube I3 will be shifted away from the deflector plate I9 therebyincreasing the size of the mixture discharge opening 29. During theseaxial movements of the mixing tube I3 its flared upper end will beguided by the group of axially extending arms 2|.

For the eificient functioning of the modulating burner II] it isdesirable to control the supply of combustion air simultaneously withthe control of the gas stream and the gas and air mixture stream. Inthe'gas burner illustrated in Fig. 1 this is accomplished by the damper34 which is connected with the lower end of the mixing tube I3 formovement therewith and controls the flow of combustion air into theburner through the air inlet opening IT. The damper 34 is here shown ascomprising a dished sheet metal disc having a central opening 34asurrounding the nozzle 25 and guided thereon. The damper can beconnected with the mixing tube I3 as by means of a plurality of spacedrods 35 so as to leave an opening or passage 36 between the damper andthe lower end of the mixing tube for the above mentioned flow ofprimary'combustion air into such lower end of the mixing tube.

When the valve element 3| and the mixing tube I3 are moved in an upwarddirection to decrease the volumes of the gas stream and the mixturestream as explained above, the damper 34 approaches the flared lower end|2a of the outer burner tube to decrease the effective size of the airinlet opening IT. This causes the volume of both primary and secondarycombustion air to be decreased. Conversely, when the valve element 3|and the mixing tube I3 are moved downcontrol compartment 44 through therestricted outlet 52 is prevented and the gas pressure on opposite sidesof the diaphragm 38 has equalized through the restricted passage 49, thespring 69 willshift the valve element 3| upwardly and hold this valveelement in its closed position. When gas is bled or permitted to escapefrom control compartment 44 through the restricted passage 52, thepressure in the control compartment drops and is overbalanced by the gaspressure in the supply compartment 45 causing down ward movement of thediaphragm 38 and a corresponding downward or opening movement of; thevalve element 3|. Increase or decrease in the flow of gas out of thecontrol compartment 44 through the restricted passage 52 results in acorresponding downward opening or upwardclosing movement of the valveelement 3|. It will accordingly be seen that by controlling the pressureof the gas in the control compartment 44, the gas pressure actuation ofthe valve ele ment -3| can be controlled in a positive and sen-l sitivemanner for modulating the gas flame.

The escape or bleeding of gas from the control compartment 44 for theabove explained purpose can be controlled by the use of any appropriatecontrol device or devices. In the modulating gas burner illustrated inFig. 1 the escape of gas from the control compartment 44 is controlledby the pilot burner unit 55 and also by the two additional controldevices H and 12. The pilot burner unit 55 and the control devices IIand 12 are disposed in a series relationship or cirj cuit, that is tosay, the gas bled from the control compartment 44 first flows to thepilot burner unit, then to the control device H and then to the controldevice 12.

The control device 1| may be a temperature responsive limit controldevice which is associated with the heating furnace F being served bythe burner unit I and hence is disposed in local relation to the burnerunit. The control device 12 may be a room thermostat which is locatedrelatively remote from the burner H) such as in a room or other space towhich heat is supplied by the burner. The control gas circuit in whichthe pilot burner unit 55 and the control devices 1| and 12 are locatedincludes the bleed conduit 54 which connects the pilot burner unit withthe restricted outlet 52 of the control compartment 44, a conduit 13which connects the control device "H with the pilot burner unit and aconduit 74 which connects the control device 12 with the control deviceH. This control circuit also includes a return conduit l Which connectsthe control device 12 with the gas escape conduit 43.

The pilot burner unit 55 is itself of novel construction and cooperateswith the main burner in anovel manner. This pilot burner unit isprovided with a burner tube 11 which is mounted on the main burner tubeI2 as by means of the bracket 18 and includes a head 19 which is mountedon the upper end of the burner tube 11. The pilot burner unit alsoincludes an auxiliary burner tube 80 which projects from the upper endof the burner tube 11 and extends through the head 19. The pilot burnerunit 55 is disposed in the secondary combustion air passage 21 of themain burner and is located therein so that the upper end of theauxiliary. burner tube 80 will occupy a position near the dischargeopening 29 of-"the main burner.

The auxiliary burner tube 89 is open at its upper end and may also haveside openings 8| therein adjacent its upper end. A gas and air mixtureis discharged continuously from the end and side openings of theauxiliary burner tube for maintaining a pilot flame Pl adjacent thedischarge opening 29 of the main burner. The burner tube 11 is providedwith one or more air inlet openings 82 and with a gas delivery nozzle83. The lower end of the auxiliary burner tube. an has openings 84therein by which it is connected with the interior of the burner tube 11to receive a gas and air mixture from the latter. The discharge of gasfrom the nozzle 83 induces a flow of air into the burner tube 71 throughthe openings 82 for mixing with such gas. A supply of gas is fedcontinuously to the pilot burner unit '55 through a conduit 85 whichconnects the gas delivery nozzle 83 with the inlet compartment 40 of thecasing through a manually adjustable control valve 85. The conduit 85 isconnected with the passage of the nozzle 83 through the groove 81 andthe inclined passages 88 formed in the plug portion 83a of the nozzle.

The head 19 which is carried by the pilot burner tube 11 also has adischarge opening 89 for discharging gas and air mixture from the tube11 and which opening surrounds the auxiliary burner tube 8|]. The head19 also has a recess 90 therein connecting the discharge opening 89 witha flame space 9| which is defined in part by a bracket portion 190. ofthe head and in part by a bimetal temperature responsive arm 92 whichoverlies the flame space. The gas and air mixture which issues from thedischarge open ing 89 and the recess 90 burns as a sustained pilot flameP2 which plays against the underside of the temperature responsive arm92. The sides of the flame space 9| are open and permit the flame P2 tospread-laterally and rise on opposite sides of the temperatureresponsive arm 92 as shown in Fig. 2.

The delivery of gas through'the nozzle 83 of the pilot burner unit 55 iscontrolled by an axially movable needle valve element 93 having a stemextension 93a on which the auxiliary burner tube 80 is mounted. Thedischarge opening 89 is controlled by a valve element 94 which is hereshown in the form of a collar carried by the axially movable auxiliaryburner tube 80. Downward or opening movement is imparted to the valveelement 93 through the auxiliary burner tube 80 by the temperatureresponsive arm 92 which has one end thereof anchored on the bracketportion 19a of the head 19 by means of the screw 95. The arm 92 extendslaterally in overlying relation to the space 9| and the free end of thisarm is in the form of a fork 96 which straddles the auxiliary burnertube 80 immediately above a transverse pin 91 carried by the latter.

In this position the temperature responsive arm 92 will be contacted bythe pilot flame P2 formed by the burning of the gas and air mixtureissuing from the opening 89 and will act to automatically maintain theflame P2 at a desired predetermined size or temperature value. Wheneverthe arm 92 cools it will be deflected downwardly causing the auxiliaryburner tube 80 and the valve element 93 to be shifted in a downwarddirection by'the pressure of the forked end 96 on the pin 91; Thisdownward movement increases the opening of the gas delivery nozzle 83thereby increasing the supply of gas for the pilot flame P2. Conversely,whenever the temperature of the arm 92' increases above a predeterminedvalue this arm will be deflected upwardly thereby releasing the pin 91and permitting the valve element 93 and the auxiliary burner tube 80 tobe-lifted by a 9. compression. spring, 99 which. is. embodiedin' thepilot. burner and located beneath thecontrol gas valve I00. This upwardmovement of the valve element 93 decreases the size of the opening ofthe delivery nozzle: 83 and thereby reduces. the supply of the gas forthepilot flamePr.

In this manner the temperature responsive arm 92 automatically controlsand varies the supply of. gas for the. pilotv flame: P2 and maintains:this gas supply at such. a: volume that an adequate but not excessiveheating of the arm 92 will.- take place. The pilot. flame PI whichburnsv from the upper end of the auxiliary burner tube 80 will burncontinuously at. approximately the same fiamesize but the pilotflametPZx will be gradually varied or modulated, as explained: above,.in: accordance with the temperature condition in.- fiuencing thetemperature responsive arm 92. As shown in Figs. 1 and 2 the arm. 92 canbe protected from the heat of the main burner flame by means of a guardI I which is disposed over this arm and is held in place by the screw95.

The lower portion ofthe pilot burner unit. 55 contains the abovementioned control valve member I00 which constitutes one of the seriescontrols for controlling thebleeding of gas from the control compartment44 of the casing II. This valve member controls-the flow of gas from theconduit 54 into the conduit 13 leading to the control device II. Duringsuch time that the pilot burner 55 is ignited, a relatively h-otcondition exists for the temperature responsive arm 92 andthis' arm willthen be deflected upwardly, as explained above; and this will permit thespring. 99 to lift the valve member I00 to its open position in whichgas can" be bled from the control compartment 44' and will" be permittedto flow into the conduit I3 to the temperature responsive. limit.control device 1 If. During the time thatthe pilot burner 55'isextinguished, the arm 92 will be relatively cool and willv be deflecteddownwardly to a position in which. the control valve member I00 willbeheld closed by the lower end ofthe valve element 93' and even thoughthe. t'emperatureresponsive'devices H and I2 should call for'operationof th main burner, theisi'gnal will not: be: transmitted to the controlcompartment 44: and the valve element 3| of the main burner will remainclosed.

The temperature responsive limlt'. control device TI may be any.suitable form? of device of this type and, in this instance, comprises abody I02 adapted to be mounted on the furnace structure l4 and having avalve passage I03 and a valve chamber I04 thereirrconnect-ing conduitlttwith the conduit. A.- valve member I05 movable-in the valve chamber I04controls the passage I '23 andis adapted to be moved toward aclosedposition in opposition. to a compression spring I06 by the bimetal'element I01 acting through the stem I08; A flexible member or bellowsI09 forms a seal for the passage through which. the stem I08 extendsand. prevents the escape of gas from the valve chamber I04 around thisstem. The actuation of t-he'valve member I05 by the bimetal element I01can be adjusted or calibrated by means of the thumb screw IIO which:varies the compression of. the spring I06.

The temperature responsive device 12 is a room thermostat or thelikecomprising a suitablev casing II2 containing a body H3 having a valvechamber I I4 therein with. which the return conduit is'connected.A-valve passage H5 is controlled by a movable valve member H6 andconnects the supply conduit 14 with the valve chamher '4. The valvemember I I Iiv is moved toward its closed. position by' a; temperatureresponsive member II! which is here showninthe form of anexpansibletemperature responsive bellows device. The bellowsdevice- I I1acts throughalever II8 which is rockable on the pivot. H and impartsmovement to a valve actuating stem I=20 in a direction to close thevalve member H6v in opposition to the compression Spring I 2 I... Theaction of theb'ellows I I! can be adjusted orcalibrated by means of theadjusting screw- I22. which carries a graduated dial I23", the latterbeing movable relative to a fixedpointer I24.

Whenever the room temperature is relatively low a contraction ofthebellows' I I1 permits the valve member I |6 to=be opened'by'the'spring I2I and this permits the bleeding of gasirom the controlcompartment 44 of the casing. I I', provided that the control valvemember I00 of the pilot burner unit 55 and the valve member I05 of thelimit control device II, are open. The escape of gas from the controlcompartment 44 causes the above explained: opening movement of theneedl'e valve element 3 I of the main burner I0 which increases thevolume of the gas stream being delivered from the nozzle 25. If" thepilot burner unit is extinguished the control valve member I00 will beheld closed, as explained above, or if the operating temperature of thefurnace F is excessive the valvemember I05 of the control device H willremain closed and; in either event;

,the opening of the valvemember I I 6 of the room thermostat will notcause bleeding ofgas from the control compartment 44 andat' this timethe pressures in the control compartment 44 and the supply compartment45 will beequalizedand the spring 69 will hold" the needle valve element3I closed. When the pilot burner-55 is lighted and the temperature ofthe furnace F'i's not excessive, the control valve members I00 and I05will be open and a modulating control-of the main burner will then becarried out by" the room thermo' statIZ;

Since the return conduit 15' connects with the conduit 43' leading tothe mixing tube 21 it will be seen that the small flow of control gaswhich is bled from the control chamber 44' and which has passed inseries relation through the valve chamber of the pilot burner unit 55,the valve chamber of the control device II and the valve chamber of thethermostat 12, will be returned" to the main burner and will be mixed"with the air stream and burned as a part of the main burner flame.

In connection with the construction and operation of the burner I0 itwill be observed that if a down-draft occurs it will travel downwardlyrelatively freely in the. annular passage 21 because the latter is inopen communication with the main combustion chamber with which theburner is being used. This movement of the down-draft will be arrestedby the damper II' which acts as a barrier thereby causing the velocityfiow of the down-draft to be converted into a pressure at this pointwhich moves upwardly into the lower end of the mixing. tube I3. Althoughsome ofthe down-draft stream may attempt to enter the upper end of themixingtube I 3- it will be met and equalized by the upward pressure.surge from the lower end. and will thus be prevented. from blowingvoutthe. gas. flame.v

Fig. 4 of the drawings. shows another modulating gas burner I30 which isgenerally similar to theburner I0 above described: but-which is of amoresimplified. construction. Theburner I30 11 comprises coaxial outerand inner burner tubes I31 and I32 having an annular secondarycombustion air passage I33 therebetween and a hollow control casing I34through which the gas is supplied to a gas delivery nozzle I35. Theouter burner tube I3I is mounted on the casing I34 by the spaced studsI35 so as to provide therebetween an inlet opening or passage I31 forcombustion air.

The upper end of the outer burner tube extends into an opening of arefractory slab I38 which may form a portion of the'wall of thecombustion chamber with which the burner is being used. A secondrefractory slab I39 is supported from the upper end of the outer burnertube in spaced relation to the slab I38. The slab I39 can be mounted onthe outer burner tube I 3I by means of the bridge member I45 havingspaced axial arms I40a which are connected with the upper end of theouter burner tube.

The inner burner tube I32 may be in the form of Venturi tube as hereshown and is mounted in the outer tube I3I by means of a group ofradially extending arms MI which extend through the inner tube and havetheir outer ends connected to the outer tube. The inner tube is disposedin axial alignment with the nozzle I35 and has its lower end inadjacently spaced relation to this nozzle so that a velocity stream ofgas being discharged through the orifice I42 of the nozzle will bedirected upwardly through the inner tube and will induce a flow ofprimary combustion air into the lower end of this tube from the airinlet opening I31. The upper end of the inner tube is disposed so thatit lies in substantially the same horizontal plane as the upper end ofthe outer tube I3I. A deflector plate I43, located adjacent the upperend of the inner tube and extending transversely thereof, defines withsuch upper end of the inner tube a discharge opening or space I45 fordischarging a velocity stream of the gas and air mixture being producedin the tube I32. The annular space between the upper ends of the outerand inner tubes I 3I and I32 forms a discharge opening I46 for secondarycombustion air.

The orifice opening I42 of the gas delivery nozzle I35 is controlled byneedle valve element I41 having a tapered portion I48 axially movable inthis orifice opening. This needle valve element also has an extensionstem portion I45 which extends through, and is guided in a sleeve I50carried by the inner ends of the arms MI. The deflector plate I43 ismounted on the upper end of the stem extension I49 so that control Imovements imparted to the needle valve element will also shift thedeflector plate for varying the size of the gas discharge opening I45and the size of the secondary air discharge opening I48.

The direction of the taper I48 of the needle valve'element is such thatwhen the latter is moved in a downward direction, that is to say in adirection inwardly of the nozzle I35, the volume of the gas stream beingdischarged from the nozzle andthesize of the orifice opening I42 will bedecreased and, conversely upward or outward movement of the taperedportion I48 will increase the size of the orifice opening and the volumeof the gas'stream being delivered therefrom. The corresponding movementsimparted to the deflector plate I43 will be such that when the volume ofthe gas stream being discharged from the nozzle orifice I42 is decreasedthe size of the mixture'discharge opening I45 and the secondary airdischarge opening I46 will likewise be decreased. On the otherhandwhenthe movement of needle valve element increases the size of theorifice I42 the corresponding movement imparted to the deflector plateI43 will increase the size of the mixture and secondary combustion airdischarge openings I and I46.

The hollow casing I34 is formed by connecte top and bottom casingsections I34a and I342) which have a flexible diaphragm I53 mountedtherebetween. This diaphragm divides the in.- terior of the casing I34into a gas supply compartment I5I and a control compartment I52. A'restricted passage I53 formed in the wallyof the casing connects thesupply and control compartments I5I and I52 and permits a pressureequalization therebetween. The size of the restricted passage I 53 canbe varied by the adjusting screw I54. The' supply compartment'I5I isconnected with a source of gas under pressure by means of the-pipe I55.I

The needle valve element I i'I which controls the orifice I42 of the gasdeliver nozzle I35, is connected with the diaphragm I55 for actuationthereby. This valve element is connected with the diaphragm by means ofa tubular stem I5'I whose lower end extends through the diaphragm and,is in open communication with the supply compartment I5I. The upperportion of the tubular stem I57 has openings I58 therein through whichthe gas from the supply compartment I5-I is delivered to the interior ofthe nozzle I35. The tubular stem portion I5! is axially movable in anopening I 59 provided in the base portion I35a of the nozzle I35. Theescape of gas through the opening I59 is prevented by a flexible sealingdia-v phragm I65 having its central portion connected with the centralportion of the main flexible diaphragm I and whose edge portion ISIla isseal.- ingly pressed against the top casing section I34a by thecompression spring I M This compression spring is preferably a taperedlow rate spring which also acts on the main diaphragm I so as tocooperate with the gas pressure in causing the desired actuation of theneedle valve element I47 and the deflector plate I43. A small breatherpassage I62 is also formed in the base portion [35a of the nozzle I35and connects the sealing space or chamber I63 surrounding the hollowstem I57 with the interior of the nozzle I35.

The control compartment 152 of the casing "I34 has an outlet or bleedconduit I35 connected therewith so that the pressure of the gas in thecontrol compartment can be varied so as to produce a desired pressuredifferential between the control compartment I52 and the supplycompartment I 5i for'actuating the diaphragm I50 and. the needle valveelement I41 connected therewith. The escape or bleeding of gas from thecontrol compartment I52 through the conduit I55 can be controlled bysuitable control devices, such as the above described limit controldevice II which would be located in local relation to the burner I35 andthe room thermostat 72" would be located at a point relatively remotefrom the burner. When either of these control devices permits the escapeof gas from the control compartment I52, the resulting pressuredifferential on oppositesides of the diaphragm I53 will cause upwardmovement thereof to thereby lift the needle v'alve element I41 andincrease the orifice opening I42 to correspondingly increase thevolumeof the gas stream being delivered by the nozzle I35. .Wheheither' of thecontrol'devices II and 72 acts to decrease or terminate the escape ofgasfrom the control compartment I52 the resultingequalization ofpressure between the 13 control and supply compartments and the ac tionof compression spring I6.I cause a down ward movement of the diaphragm.I50. and a corresponding downward or closing movement of the valveelement I4'I..

In the operation of. the burner I30 as just described it will beobserved that the movements imparted. to the. needle valve element IE1and. to the deflector plate I43 will be such as to cause gradualincrease or decrease in the size of. the gas delivery orifice I42 and inthe size of the mix.- ture discharge opening I45 and also in thesecondary combustion air discharge opening I46. This gradual variationin the. size of theseopenr ings produces a desired modulation of the gasflame. formed by the combustion. of the gas and air mixture .beingdischarged through the opening I45; The gas which isbled from. thecontrol compartment I52 can be returned to the burner and dischargedinto the lower end. of the mixing. tube I32 by the return conduit. I66.

A pilot burner IG'Imay be provided adjacent the main burner I30 and, inthis instance, is of a simple construction comprising merely a gas andair mixing tube I68. extending axially along thev outside of the outerburner tube I3I and mounted thereon by means. of the brackets I69. The?pilot burner I6! also includes a gas delivery nozzle I10 whichdischarges av stream of. gas upwardly through tube I68 but is spacedfrom the lower end. thereof to permit. an induced flow or air to enterthis tube for mixing with the gas stream.. The. nozzle I10 is connectedwith the supply compartment II of the casing I34; and the flow of gasthrough this. nozzle can. be regu lated by means of the adjustablevalve. key MI; The upper end, of the pilot: burner I61 extends throughthe refractory slab I33 and is located opposite the discharge. openingI45 so that a pilot flame burnin continuously from the upper end of thetube I68 will be in adjacent relation to the discharge openingforigniting, the mixturestream issuing therefrom.

In the modulating gas burners I0 and; I30 as described. above it shouldbe noted that the gas: is

discharged from the nozzle as a velocity stream which induces a flow ofprimary combustion. air into the mixing tube and. the resulting gas. andair mixture is. discharged from the burner opening. as a velocitymixture stream. When the vol ume of gas being discharged from the nozzleis varied, the. size of the mixture discharge. opening and the amount ofcombustion air are varied simultaneously and in. corresponding relation.This provides for a gas and air mixture in proper proportions for asubstantially complete combustion and a substantiallyconstant flue gasanalysis throughout the full range of burner operation, and also insuresa velocity discharge of the mixture from the burner opening which at alltimes prevents the occurrence of a backfire. Even though the volumes ofthe gas stream and mixture stream are varied the discharge velocity" forthese streams is maintained and the burners have what can be referred toas a substantially one hundred percent turn down ratio. Because of thesecharacteristics the main burner flamecan be gradually increased ordecreased in accordance with heat requirements and the burning of thegas will; take place safely and efficiently throughupp ends of theburnertubesm-and I32 d r prevents down-drafts from. entering thesetubes. andhence, the gas flame is not likely to be blown out. The inner tube I32is particularly well shielded by the deflector M3 and any portion of:the down-draft stream which enters the outer tubeI3I canpass freelytherethroughwithout materially affecting the gas stream or the flame.

Although the improved gas burner has been disclosed. herein to adetailed extent, it should be understood that the invention is notintended to be correspondingly limited in scope but includes all changesand modifications coming within the scope of the appended claims.

Having thus described our invention, we claim: 1. In a gas burner, ahousing comprising a casing and a main burner tube connected therewith,a mixing tube member located in said main burner tube and extendingsubstantially coaxially thereof, a deflector member, said mixing tubemember having an air inlet at one end thereof and a discharge opening atits other end for discharging a gas and air mixture, said deflectormember being located adj acent to and extending transversely of saidother end of said mixing tube member and cooperating therewith indefining said discharge opening, one of said members being movablerelative to the other axially of said main burner tube for varying saiddischarge opening, a gas delivery nozzle adapted to discharge a velocitystream of gas in said mixing tube member axially thereof for mixing with'air from said air inlet, means for supplying gas under pressure to saidnozzle, a. movable valve element controlling the delivery of gas fromsaid nozzle, means connecting said one memberwith said valve element.for movement coniointly with the latter, gas pressure responsivediaphragm means in said casing. and. operable to ca se such conjointmovement of said one member and valve element, and pressure regulatingvalve means, in said casing for controlling the pressure of the gasacting. on said pressure responsive means;

2. A gas burner of the character described comprising a burner tubehaving an air inlet, a

mixing tube member having one end located to receive airfrom said inlet,said mixing tube. member being disposed in said burner tube and spacedfrom the wall of the latter to provide therebetween a passage forsecondary air from said: air inlet, a gas delivery nozzle adapted todischarge gas axially in said mixing tube memher. for mixing with airfrom said inlet, a deflector member spaced from the other end of saidmixi-ngtube member to provide therebetween a discharge opening for a gasand air mixture, one of said-members being shi ftable for varying saidvdischarge opening, a movable valve element'- cooperating; with saidnozzle for controlling the delivery of gas through the latter, a dampercontrolling. the flow of airthroughsaid inlet",- said one member anddamper being adapted for'movemerit proportionately with said:valveelement, a

hcllowcasing having supply con trol: comps-rt m'cnts therein and. arestricted passage: connect ing; said. compartments. with each other; adia: phragm in said casing between said compart-' ments and: operablyconnected with said valve element for: causing. actuation of the valve:ele merit, said. one member and-said damper in re: sponseto a:pressure'differential between sal'di compartments, means forsupplyinggas: under pressure to: saidinozzle; and having communicationwith said supply compartment; and; means for discharging gas from saidcontrol chamber at a'controlled rate for creating said pressuredifferential. i

3. A gas burner of the character described comprising, a casing, aburner tube having one end thereof connected with said casing, a mixingtube in said burner tube and spaced "from the wall of the latter toprovide an air passage .therebetween, a deflector mounted on the otherend of said burner tube and extending transversely of one end of saidmixing tube and spaced therefrom so as to provide therebetween adischarge opening for a gas and air mixture, said mixing tube having anair inlet at its other end and being shiftable relative to saiddeflector for varying the size of said discharge opening, a gas deliverynozzle adapted to discharge a velocity stream of gasaxially of saidmixing tube and toward said discharge opening, arnovable valve .elementcooperating with said nozzle for controlling the delivery of gastherefrom and having operative connection with said mixing tube forsimultaneously shifting the latter, and gas pressure responsivediaphragm means in said casing and connected with said valve element forcausing the simultaneous actuation of said valve element and mixingtube.

4. A-gas burner comprising a casing having an inlet for gas underpressure and a gas deliv ery nozzle connected with said inlet to be sup-.plied therefrom, a. burner tube having an air inlet end connectedwithsaid casing and pro- .vided with an air inlet opening, a deflectorcarried by said burner tube, a movable valve needle cooperating withsaid nozzle for controlling the delivery of gas therefrom, a mixing tubein said burner tube and disposed so that gas is discharged thereinto bysaid nozzle for mixing with air from said air inlet, said mixing tubehaving one end thereof spaced from said deflector to provide a dischargeopening therebetween for a gas and air mixture, means connecting saidmixing tube with said valve needle for movement by the latter relativetothe deflector for varying said discharge opening, and gas pressureresponsive diaphragm 'fneans in said casing and adapted to causesimultaneous actuation of said valve needle and mixing tube. r

5. Ages burner comprising a casing having an inlet for gas underpressure and a gas delivery nozzle connected with said inlet to besupplied therefrom, a burner tube having an air inlet end connected withsaid casing and provided with an air inlet opening, a deflector carriedby said burner tube, a movable valve needle cooperating with said nozzlefor controlling the delivery of gas therefrom, a mixing tube in saidburner tube and disposed so that gas is discharged thereinto by saidnozzle for mixing with air from said air inlet, said mixing tube havingone end thereof spaced from said deflector to provide a dischargeopening therebetween for a gas and air mixture, means connecting saidmixing tube with said valve needle for movement by the latter relativeto'the deflector for varying said discharge opening, a movable aircontrol member controlling the flow of air through said air inlet, meansconnecting said air control member with said valve needle, and gaspressure responsive diaphragm means in said casing and operable to causeactuation of said valve needle, mixing tube and air control membersimultaneously.

6'. A gas burner comprising a burner tube having an air inlet openingand a discharge opening,

16 a mixing tube in said burner tube and spaced from the wall thereof toprovide a passage therebetween for secondary air, said mixing tubehaving a discharge opening lying in substantially the same plane as thedischarge opening of said burner tube, a gas delivery nozzle adapted todischarge gas into said mixing tube for mixing with air from said airinlet opening, a movable valve needle cooperating with said nozzle forcontrolling the discharge of gas therefrom, a control member disposedadjacent to and extending transversely of the discharge openings of saidburner tube and mixing tube, means connecting said control member withsaid valve needle for movement thereby relative to said burner tube andsaid mixing tube for varying said discharge openings, and means forsupplying gas under pressure to said nozzle including gas pressureresponsive diaphragm means for causing actuation of said valve needleand control member simultaneously.

7. A modulating gas burner comprising a bottom casing having atransverse top wall, an upright burner tube supported by said casing andextending upwardly from said top wall, a mixing tube member extendingupwardly within said burner tube in substantially coaxial relationthereto and being spaced from said burner tube to define therebetween anupright annular passage for secondary combustion air, said burner tubebeing open at its upper end and having an air inlet opening at its lowerend adapted to supply said secondary combustion air to said annularpassage, said mixing tube member having a substantially Venturi shapedpassage and being open at its upper and lower ends and having its lowerend disposed above said air inlet opening so as to receive primarycombustion air there from, a deflector member extending transversely ofand spaced from the upper end of said mixing tube member and'cooperating therewith in defining an annular discharge opening for a gasand air mixture, said bottom casing having gas supply and controlcompartments therein and a restricted passage connecting saidcompartments with each other, a diaphragm in said bottom casing betweensaid compartments and being movable in response to a pressuredifferential therebetween, a gas delivery nozzle carried by said topwall and disposed so as to discharge a velocity stream of gas from saidsupply compartment upwardly into the lower end of said mixing tubemember for inducing a flow of said primary combustion air thereinto fromsaid air inlet, a valve element axially movable in said nozzle forcontrolling the discharge of gas therefrom and hav-.- ing its lower endconnected with said diaphragm for actuation thereby, one of said membersbeing movable in the direction of the axis of said burner tube andrelative to the other of said members for varying the size of saidannular discharge opening, means connecting said one member with saidvalve element to vary said discharge opening proportionately with theopening and closing of the valve element, and means for discharging gasfrom said control compartment at a controlled rate for creating saidpres sure differential.

PAUL F. SWENSON. MILTON F. PRAVDA.

(References on following page) I 7 REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Merrill Oct.-8, 1889 Elliott May27, 1902 Mavrogordato Nov. 21, 1911 Killam Mar. 31, 1914 AndersonMa'y29, 1923 Morgan Jan-15, 1924 Ronstrom Nov. 11, 1924 McMullen Aug.25, 1931 Hegwein et a1 July 31, 1935 Number Name Date Leahy Dec. 29,1936 Engels Apr. 5, 1938 Kronmiller May 23, 1939 Long Nov. 25, 1941Jones Aug. 31, 1943 Higley Nov. 7, 1944 Hopkins June 5, 1945 Higley May6, 1947 FOREIGN PATENTS Country Date Great Britain Feb. 4, 1921 FranceNov. 19, 1925

